1. Field of the Invention
The present invention relates to an electrostatic chucks.
2. Description of the Related Art
An electrostatic chuck is used as a mounting base for fixing (holding) a workpiece in various processes of manufacturing a semiconductor devices. Here, the term “workpiece” mainly corresponds to a wafer or a reticle.
Besides fixing the wafer, the electrostatic chuck can be used for efficiently removing heat created in the process from the wafer so as to maintain the temperature of the wafer substantially constant. In order to increase the cooling effect on the wafer, the electrostatic chuck is arranged on a cooling device. In order to remove heat from the wafer to be adsorbed by the electrostatic chuck, a pore (passage) has been provided in the electrostatic chuck for a back side gas, such as Helium (He), to flow therethough to the back side of the wafer (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2000-315680). Depending on application, there is a requirement to improve the cooling effect on the wafer.
When the wafer is mounted on the electrostatic chuck and is then processed by plasma etching, the etching rate is likely to be different on the wafer surface due to on-uniformity of the plasma. As a means for solving such problem, it has been required to increase the plasma density.
The higher plasma density increases heat flow into the wafer. The cooling efficiency needs to be improved by reducing the thickness of the electrostatic chuck and the distance between the metallic cooling device and the wafer mounting surface. In this case, arcing can be caused near the pores in which the back side gas flows. When the arcing occurs, problems such as deposited particles, wafer damage, and breakage of the electrostatic chuck may occur.